Note: Descriptions are shown in the official language in which they were submitted.
WO 2021/102432
PCT/US2020/061855
A METHOD FOR REDUCING THE VISCOSITY OF HEAVY OIL FOR EXTRACTION,
TRANSPORT IN PIPES, AND CLEANING THEREOF
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] The present application claims priority to U.S. Provisional Patent
Application
No. 62/939,169, filed November 22, 2019, the entire contents of which is
hereby
incorporated herein by reference for all purposes.
STATEMENT REGARDING FEDERALLY SPONSORED
RESEARCH OR DEVELOPMENT
[0002] Not applicable.
BACKGROUND
Field of the Disclosure
[0003] The disclosure relates to viscosity reduction of a hydrocarbon, wherein
the
reduction in viscosity of the hydrocarbon may aid in the extraction, removal,
or transport of
the hydrocarbon. The disclosure more particularly relates to reducing the
viscosity of an
oil, wherein the oil may be, but not limited to heavy oil and extracting for
example
underground viscous heavy oil, the transportation thereof by long distance
pipes, and
cleaning of such oil. The disclosure also relates to viscosity reduction of
oil sands, light
sweet crude, and shale oil. The disclosure particularly relates to
compositions comprising
highly reactive metal, oxides, and salt particles that react with water and
oil to produce
large amounts of alkaline, gas, and heat for reducing the viscosity of, for
example heavy oil
and aid in the recovery of oil from: underground formations, above ground oil-
sands, its
transport through pipes, and methods of making and using the same.
Background of the Disclosure
[0004] Employing nanotechnology for enhanced oil recovery (EOM is believed to
provide revolutionary "green" or "zero emissions" solutions to previously
intractable
problems in the oil and gas industry. Nanotechnology has been envisioned to
transform
the petroleum industry. Numerous research on nano-EOR have been done in the
past
few years and shown promising results for improving oil recovery. Injected
nanoparticles
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and/or nanosheets are believed to be able to form adsorption layers on the top
of the
grain surface. The adsorptions layers then alter the wettability of the rock
and reduce
the interfacial tension. Thus, the adsorption of nanoparticles and/or
nanosheets is one
of the important aspects that needs to be understood for a successful EOR
implementation. Various types of nanoparticles and/or nanosheets can improve
oil
recovery through several mechanisms such as wettability alteration,
interfacial tension
reduction, disjoining pressure and mobility control. Parameters such as
salinity,
temperature, size, and concentration are substantial for nano-EOR.
Nanoparticles
and/or nanosheets can improve the oil recovery significantly after the primary
recovery
period.
[0005] As projected by the Organization of the Petroleum Exporting Countries
(OPEC)
in 2019, the expected global oil demand will increase to 110.6 million barrels
per day in
2040. As reserves of conventional light oil become depleted, recovery of
viscous oil is
urgently needed to meet increasing energy demands worldwide. Hydrocarbon or
fossil
fuel plays a major role in today's human civilization. During
industrialization era coal was
the dominant source, until today oil and gas are the major fuel for all
transportation
sectors. Hydrocarbon is still predicted to be the primary source of energy for
the
upcoming decades, and the consumption of hydrocarbon will significantly
increase over
the years. However, there are numerous oil and gas fields in the world which
have
already reached plateau period and the production will likely decline. To meet
the
energy demand for the next decades, methods for extracting residual
hydrocarbon
trapped in reservoir need to be developed economically. Based on U.S
Department of
Energy data, 67% of total oil in the United States of America will remain in
the reservoir
because of the limitation of the technology to extract residual hydrocarbon.
There are
various enhanced oil recovery (EOR) technologies which have been applied and
were
proven to increase hydrocarbon recovery significantly such as thermal methods,
miscible methods, chemical methods, as well as some new technologies
(microbial, low
salinity flooding). More recently, nanotechnology is proposed to be one of the
promising
EOR methods since it can penetrate the pore throat easily and change the
reservoir
properties to increase the oil recovery. Nanotechnology has shown its
potential to
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revolutionize the petroleum industry for both upstream and downstream sectors
in the
recent years.
[0006] As the molecular structure of oil becomes more complex, the oil becomes
heavier and more viscous, causing flow problems at regular reservoir
conditions and
exhibiting strong temperature-dependent behavior. Due to the variety of both
the heavy
oil viscosities and the reservoir locations around the world, different
recovery
technologies must be applied. Current state-of-the-art technologies fall into
two
categories, surface mining and in situ recovery. Surface mining refers to the
mining of
oil sands on land, followed by extraction of the oil through dilution with n-
pentane or n-
heptane. Although this method has been used for decades, there are increasing
concerns regarding disposal of tailings, water consumption, etc.
[0007] Since most heavy oil resources are in the subsurface, much greater
attention
has been focused on in situ recovery methods by both industry and academic
researchers. In recent years, both non-thermal and thermal methods have been
developed, with respective advantages and disadvantages. Generally, the non-
thermal
methods, including cold production with sands, vapor extraction (VAPEX),
chemical
injection, miscible flooding, etc., can be used for thin layers of formation,
but are limited
to such shallow formation and to relatively light (< 200 cP) viscous oils.
Although
thermal methods like in situ combustion, steam flooding, cyclic steam
stimulation, etc.,
can achieve a higher recovery factor for more viscous oil, especially steam-
assisted
gravity drainage (SAGD) with a potential recovery factor of more than 70%,they
have
the strict requirement of thick formation for economic production, and their
economic
feasibility also largely depends on the market oil price. In addition, to
produce the steam
required for these thermal methods, fuel must be consumed, such as by burning
natural
gas, resulting in considerable CO2 emissions. Therefore, seeking alternative
techniques
to overcome the limitations mentioned above is of great importance (see: Guo,
K.; Li, H.
L.; Yu, Z. X., In-situ heavy and extra-heavy oil recovery: A review, Fuel 185,
886-902
(2014), lstchenko, C. M.; Gates, I. D., SPE Journal 19, 260-269 (2014);
Ahmadi, M. A.;
Zendehboudi, S.; Bahadori, A.; James, L.; Lohi, A.; Elkamel, A.; Chatzis, I.,
Ind. Eng.
Chem. Res. 53, 16091-16106 (2014). Ahmadi, M.; Chen, Z. X., Adv. Colloid
Interface
Sci. 275, 102081 (2020); Orr Jr. F. M.; Taber, J. J., Science 224, 563-569
(1984);
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Chopra, S.; Lines, L.; Schmitt, D. R.; Batzle, M., Heavy-Oil Reservoirs: Their
Characterization and Production," Geophysical Developments Series: 1-69
(2010);
Biyouki, A. A.; Hosseinpour, N.; Nassar, N. N., Energy Fuels 32, 5033-5044
(2018);
Sun, F. R.; Yao, Y. D.; Chen, M. Q.; Li, X. F.; Zhao, L.; Meng, Y.; Sun, Z.;
Zhang, T.;
Feng, D., Energy 125, 795-804 (2017); Wang, Y. Y.; Zhang, L.; Deng, J. Y.;
Wang, Y.
T.; Ren, S. R.; Hu, C. H., J. Petrol. Sci. Eng. 151, 254-263 (2017);
Mukhametshina, A.;
Kar, T.; Hascakir, B., SPE Journal, 21, 380-392 (2016)). Current technologies
thus
suffer from low efficiency, high cost, and environmental concerns, as well as
the
requirement of strict formation conditions, and further attempts to use
nanotechnology
in oil extraction have thus far been recognized to have only auxiliary
effects, such as in
modifying the crude oil's rheology and serving as catalysts to upgrade the
crude oil
during the steam process( see: Taborda, E. A.; Franco, C. A.; Ruiz, M. A.;
Alvarado, V.;
Cortes, F. B., Energy Fuels 31, 1329-1338 (2017); Saha, R.; Uppaluri, R. V.
S.; Tiwari,
P., Ind. Eng. Chem. Res. 57, 6364-6376 (2018); Alade, 0. S.; Shehri, D. A. A.;
Mahmoud, M., Pet. Sci. 16, 1374-1386 (2019); Wang, D. R.; Xu, L.; Wu, P., J.
Mater.
Chem. A. 2, 15535-15545 (2014); Lin, D.; Feng, X.; VVu, Y. N.; Ding, B. D.;
Lu, T.; Liu,
Y. B.; Chen, X. B.; Chen, D.; Yang, C. H., Appl. Surf. Sci. 456, 140-146
(2018); and
Yeletsky, P. M.; Zaikina, 0. 0.; Sosnin, G. A.; Kukushkin, R. G.; Yakovlev, V.
A., Fuel
Process. Technol. 199, 106239 (2020)).
[0008] Thus, large amounts of heavy oils are yet to be extracted, especially
extra
heavy oil and a method to extract underground heavy or extra heavy oil
efficiently and
economically is urgently needed. Disclosed herein is such a new method to
reduce the
viscosity of underground viscous heavy oil efficiently and economically for
ease of
extraction and addresses the above laid out shortfalls of conventional
methods.
BRIEF SUMMARY OF DISCLOSURE
[0009] Disclosed herein, in one embodiment is a composition for reducing the
viscosity
of oil, comprising: a reactive particle; a solvent and a polymer; and wherein
the reactive
particle is between 1 nm and 1000 microns in size and is dispersed within said
solvent,
and wherein the composition reacts with water and oil to lower oil viscosity
and facilitate
extraction from a body. In another embodiment a composition for reducing the
viscosity
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of oil is disclosed wherein the composition comprises a reactive particle; and
solvent
and wherein the reactive particle is between 1 nm and 1000 microns in size and
is
dispersed within said solvent, and wherein the composition reacts with water
and oil to
lower oil viscosity and facilitate extraction from a body. In some embodiments
the body
is a hydrocarbon comprising formation, in other embodiment the body is man
made,
such as in pipes, or machinery, in some embodiments the body is above ground,
in
other embodiments the body is below ground. In one embodiment the body is an
above
ground sand-oil formation. In a further embodiment the body is one of an oil
well, a
below ground oil well, or a deep oil well.
[0010] In some embodiments, the reactive particle comprises at least one of
VO, Ni,
Fe, Li, Na, K, Rb, Cs, Mg, Ca, Sr, Ba, B, Al, Ga, an oxide, sulfate, nitride,
or phosphide
thereof.
[0011] In one embodiment is a composition for reducing the viscosity of heavy
oils for
ease of extracting viscous heavy oil, comprising a reactive particle; a
solvent; and/or a
polymer; wherein the metal particle is between 1 nm and 1000 microns in size
and is
dispersed within the solvent, and wherein the composition reacts with water
and oil to
lower oil viscosity and facilitate extraction from an underground formation;
wherein in
some embodiments the reactive particle comprises at least one of VO, Ni, Fe,
Li, Na, K,
Rb, Cs, Mg, Ca, Sr, Ba, B, Al, Ga, an oxide, sulfate, nitride, or phosphide
thereof;
wherein in some further embodiments the reactive particle is a size reduced
particle
wherein the particle is reduced in size by a mechanic method, wherein the
mechanical
method is ball milling, or blending. In other embodiments of the composition
disclosed
herein, the solvent is selected from silicone oil, hexane, heptane, toluene,
liquid wax, or
any organic solvent which can prevent the particles from contact with water
and oxygen;
wherein in some other embodiments the polymer is a hydrophobic polymer, and
wherein the polymer stabilizes the reactive particle dispersed within the
solvent; wherein
in some embodiments the polymer can has a melting point of about 50 -C, and in
a
further embodiment the polymer is low viscous engine oil.
[0012] In another embodiment, disclosed herein is a method of making a
composition
for reacting with viscous heavy oil; ball milling or blending a metal particle
and
producing metal particles, wherein the ball milled, bead milled or blended
metal particles
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are between 1 nm and 1000 microns in size; dispersing the ball milled, bead
milled or
blended metal particles in a solvent and forming a dispersion; and mixing a
polymer with
the dispersion to form a polymer stabilized dispersion. In a further
embodiment,
disclosed herein is a method of reducing the viscosity of heavy oil
comprising: adding a
composition comprising a highly reactive metal particle; a solvent; and a
polymer to an
oil of a first viscosity; reacting the composition within the oil and reducing
the viscosity of
the oil to produce an oil with a lower viscosity. In still further embodiment,
disclosed
herein is a method of extracting oil from a formation comprising adding a
composition
comprising a highly reactive metal particle; a solvent; and a polymer to a
formation
comprising an oil of a first viscosity; reacting the composition within the
oil and reducing
the viscosity of the oil to produce an oil with a lower viscosity, and
extracting the oil with
the lower viscosity from the formation; wherein in some embodiments the oil is
heavy or
extra heavy oil; wherein the highly reactive metal particle is ball milled,
bead milled or
blended, and is between 1 nm and 1000 microns in size; and wherein in other
embodiments the method is scalable and economical.
[0013] In some embodiments of the method disclosed herein the composition is
injected into an oil well or underground formation comprising oil or oil
transport pipe; in
other embodiments the reacting further comprises reacting with water comprised
within
the formation, and wherein the reaction is exothermic and reduces the
viscosity of the
oil; in some other embodiments of the method disclosed herein reacting further
comprises the formation of metal hydroxides which further react with organic
acids
comprising in the heavy oil, and forming in situ surfactants, wherein the
surfactant lower
oil/water interfacial tension to form an emulsion; in some further embodiments
of the
method disclosed herein reacting further comprises the formation of hydrogen
gas in-
situ in the oil well, which may be benefit for increasing reservoir energy,
cause a
viscosity reduction by the miscible with heavy oil, and upgrade oil quality by
inducing
hydrogenation reactions, and in some still further embodiments of the method
disclosed
herein the polymer comprising the composition acts as a dispersant of the
particles in
order to reduce the viscosity of the heavy oil comprising the well formation,
and in other
embodiments of the method, adding is by injection, or under pressure, and
wherein the
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adding may occur after an injection of water, or before an injection of water
into the well
or formation.
[0014] In another embodiment a method of making a sodium nanofluid is
disclosed,
the method comprising a first mixing of a sodium metal and silicone oil,
wherein the first
mixing is for a first time (TI) at a first speed (S1), followed by a second
mixing of said
metal and oil for a second time (T2) at a second speed (82), wherein the first
mixing the
second mixing is by a mechanical shear force; and wherein 81<52, and TI <T2,
wherein
the first followed by the second mixing form a sodium nanofluid, and wherein
the
sodium nanofluid is cooled at five minute intervals during each of the first
mixing and
said second mixing. In some embodiments T1 may be one of about 1, 2, 3, 4, 5,
6, 7, 8,
9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28,
29, 30, 45, 60
minutes; and in some embodiments T2 may be one of about 2, 3, 4, 5, 6, 7, 8,
8, 10, 11,
12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30,
45, or 60
minutes. In a further embodiment S1 may be 10, 20, 30, 40, 50, 60, 70, 80, 90,
100,
150, 200, 250, 300, 350, 400, 50, 1000, 10000, or 100000 rpm; and 82 may be
one of
11, 20, 30, 40, 50, 60, 70, 80, 90, 100, 150, 200, 250, 300, 350, 400, 50,
1000, 10000,
or 100000 rpm.
BRIEF DESCRIPTION OF THE DRAWINGS
[0015] Figure 1 depicts: a) ball milled, bead milled or blended sodium Metal
in an
embodiment of a liquid, such as silicone oil, engine oil, or mineral oil, or
vegetable oil, or
liquid wax, or any other liquid; b) an image showing reduced size of sodium
metal
particles of an exemplary embodiment of the present disclosure;
[0016] Figure 2 depicts separation of sodium from silicone oil, or engine oil
of an
exemplary embodiment of the present disclosure, wherein separation occurred by
centrifugation;
[0017] Figure 3 depicts sodium particles dispersed in organic solvent in an
exemplary
embodiment of the present disclosure;
[0018] Figure 4 depicts extra heavy oil as used in embodiments described
herein;
[0019] Figure 5 depicts extra heavy oil viscosity reduction tests at room
temperature of
an exemplary embodiment of the present disclosure;
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[0020] Figure 6 depicts a comparative study of extra heavy oil viscosity
reduction tests
at room temperature of an exemplary embodiment of the present disclosure;
[0021] Figure 7 depicts: a) a schematic of sodium nanosheets produced using a
household blender by for example by mixing in silicone oil; b) a visual
stability
evaluation at 25 C in silicone oil and in a mixture of silicone oil and
kerosene; c) a
depiction of test-dependent XRD measurements of synthesized sodium nanosheets
in
silicone oil; d) an AFM image of synthesized sodium nanosheets in silicone oil
with
height profiles at three different positions; and e) distribution of
hydrodynamic diameters
of the sodium nanofluid detected by a light scattering method;
[0022] Figure 8 depicts: a) an image of the extra-heavy oil; b) a frequency-
dependent
loss modulus, storage modulus, and complex viscosity of the extra-heavy oil
measured
at 25 C by a rotational rheometer; b) a schematic illustration of the sand-
pack flow
apparatus, and sodium nanofluid is used to recover the extra-heavy oil, which
is initially
mixed with zirconium oxide balls and packed as a column 7 cm long with a 2.765
cm
diameter;
[0023] Figure 9 depicts: a) an initial temperature of 1 gram of extra-heavy
oil mixed
with 40 mg of sodium nanosheets dispersed in 0.5 mL kerosene; b) the maximum
temperature reached following reaction triggered by injection of 0.3 mL water
in the
same fluid system; c) the initial state of 1 gram of extra-heavy oil mixed
with 40 mg
sodium nanosheets dispersed in 0.2 mL kerosene/silicone oil (1:1 volume
ratio); and d,)
shows the injection of 0.2 mL water which causes the extra-heavy oil system to
swell
after a very short time;
[0024] Figure 10 depicts the normalized ratio of maximum sodium peak to the
maximum sodium hydroxide peak for different rounds of XRD testing. The
normalization
is based on the results of the first test round;
[0025] Figure 11 depicts the surface color evolution of ZrO2 balls after three
stages of
sodium nanofluid injections;
[0026] Figure 12 depicts: a) a fluid systems of 1 gram of extra-heavy oil
mixed with 10
mL water and different concentrations of sodium nanosheets dispersed in 0.5 mL
kerosene/silicone oil (1:1 volume ratio); b) a magnified image of the dashed
red box in a
obtained by an optical microscope, wherein the inset depicts the emulsion type
that was
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determined by injecting several drops of emulsion into kerosene; and c)
depicts the
demulsification of the fluid system using 40 mg sodium nanosheets and its
viscosity at
25 'C.
DETAILED DESCRIPTION OF DISCLOSED EXEMPLARY EMBODIMENTS
[0027] The following discussion is directed to various exemplary embodiments
of the
invention. However, the embodiments disclosed should not be interpreted, or
otherwise
used, as limiting the scope of the disclosure, including the claims. In
addition, one skilled
in the art will understand that the following description has broad
application, and the
discussion of any embodiment is meant only to be exemplary of that embodiment,
and
that the scope of this disclosure, including the claims, is not limited to
that embodiment
[0028] The drawing figures are not necessarily to scale. Certain features and
components herein may be shown exaggerated in scale or in somewhat schematic
form
and some details of conventional elements may be omitted in interest of
clarity and
conciseness.
[0029] As used herein, nanoparticles may comprise nanosheets. The
nanoparticles
may be irregular in shape, or regular in shape, or combinations thereof.
[0030] In the following discussion and in the claims, the terms "including"
and
"comprising" are used in an open-ended fashion, and thus should be interpreted
to mean
"including, but not limited to...." As used herein, the term "about," when
used in
conjunction with a percentage or other numerical amount, means plus or minus
10% of
that percentage or other numerical amount. For example, the term "about 80%,"
would
encompass 80% plus or minus 8%. References cited herein are incorporated in
their
entirety by such reference.
[0031] Heavy oil is generally accepted as oil with high viscosity due to the
larger
proportion of high molecular weight constituents in comparison with
conventional crude
oil. More precisely, crude oil is classified into different types by using its
American
Petroleum Institute (API) values:
141.5
API = _____________________________________________________________ SG
131.5
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wherein SG is the ratio of oil density to water density.
[0032] For heavy crude oil, the API value is between 10 and 20. When the value
is
less than 10, the oil becomes extra heavy. The resources of heavy oil are
abundant and
comprises about five times that of the conventional oil reserves.
[0033] The nanomaterials disclosed herein are made by a simple, scalable, and
inexpensive methods that may allow for surface transportation and injection;
b) the
nanomaterials are small enough for transport into rock pores without
significant damage
to the formation; c) the nanomaterial system has a high oil recovery factor
and may
result in a net profit; and d) the overall process from material synthesis to
post-treatment
may have a low environmental impact. Herein disclosed are examples of such
nanomaterials, compositions thereof, and methods of using such nanomaterial
compositions to lower solution viscosity, such as but not limited to the
viscosity of oil,
including heavy oil, and thus allow movement, and extraction of the same,
through or
from any body, particularly the extraction of heavy oil from a bed or rock
formation.
[0034] One embodiment disclosed herein is drawn to making and dispersing
highly
reactive particles (ranging in size from nanonneters to micrometers) in non-
water and
oxygen containing liquids, wherein the particles may also be wrapped in a low
melting
point polymer that will disassociate from the particles at above 50 C;
between 50 C
and 60 C; between 60 C and 70 C; between 70 C and 80 C; between 80 C and
90 C; and between 90 C and 100 C. These particles are made by milling one or
more
of Li, Na, K, Rb, Cs, Mg, Ca, Sr, Ba, B, Al, Ga, their oxides, or a further
material such as
salt such as Mg2SO4 (that may release a large amount of gas and heat when it
encounters with water) into liquids of non-water and oxygen containing liquids
such as a
solution, an oil, a heavy oil, engine oil, mineral oil, vegetable oil, liquid
wax, etc.
[0035] The particles, and methods described herein, in some embodiments may
generate multiple effects on the heavy oil in situ, such as viscosity
reduction and oil
quality upgrading due to the in-situ generation of a large amount of hydrogen
gas, heat,
and induction of a basic environment.
[0036] In some embodiments, bulk metal or metal oxide or salt materials are
firstly
reduced to nanometer-micrometer in size in an environment without air and
water, such
as milling or blending in viscous oil like silicone oil, engine oil, mineral
oil, vegetable oil,
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liquid wax, etc. for a time period of a few minutes to a few hours, such as
between 5
minutes to 600 minutes, 10 minutes to 500 minutes, 20 minutes to 400 minutes,
30
minutes to 200 minutes, 45 minutes to 100 minutes, 60 minutes to 120 minutes;
and 1
minute to 60 minutes.
[0037] After size reduction, high concentrations of particles are dispersed in
solvents
such as pentane, hexane, heptane, toluene, etc. These solvents may also reduce
heavy
oil viscosity. Meanwhile, polymer(s) may be added to form a core/shell
structure in order
to increase the colloidal stability and to delay reaction with water and thus
may in some
embodiments function as a protecting agent. The highly concentrated dispersion
is then
injected into reservoirs either with or in some embodiments, without a pre-
injection of
liquid to prevent the immediate reaction of the particles with existing water
in the well. In
another embodiment, additional water is then further injected into the
reservoir to push
the oil which now comprises a significantly reduced viscosity, to ground
level.
[0038] The reactions between these metal or metal oxide or metal salt
particles
liberate three products: hydrogen, heat, and hydroxide, all of which, in some
embodiments significantly reduce the viscosity of oil. Metal hydroxides such
as NaOH,
KOH, etc., when generated in-situ may read with organic acids comprised within
heavy
or extra heavy crude oil_ In this way, surfactants are produced in situ which
may lower
the interfacial tension, benefiting in one embodiment the flow of oil from the
rock bed.
Furthermore, hydrogen gas generated in some embodiments may be miscible with
heavy oil to also reduce the viscosity. Under certain other embodiments and
conditions,
hydrogen gas may react with the unsaturated components of heavy crude oil via
hydrogenation reactions, which upgrades the quality of oil.
X + H20 ¨> XOH + H2 heat where X is a metal such as Li, Na, K, ...
XO + H20 ¨> XOH + heat, where X0 is metal oxide L120, Na2O, K20 ...
MgSO4 + H20 ¨4 MgSO4.mH20 + heat, where m can be in a range of 1 and 10
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[0039] This method is facile to operate and also economic, as compared to
current
methods known in the art.
EXAMPLES
[0040] One such example of the nanomaterial disclosed herein are sodium
nanofluids.
The sodium nanofluids disclosed herein display outstanding performance for
extra-
heavy oil recovery without additional heat input. In sand-pack experiments at
room
temperature, they were found to achieve a recovery factor of more than 80% for
extra-
heavy oil with viscosity of over 400,000 cP as received. A sodium nanofluid as
disclosed
herein in one embodiment was produced using a household blender, making its
synthesis simple, fast, and inexpensive. In principle, the excellent recovery
factor for
extra-heavy oil is based on the reaction:
2Na + 2H20 ¨ 2Na0H + Hy. + heat
[0041] This reaction utilizes multiple industrial chemicals to release a
substantial
amount of heat, which may therefore reduce the viscosity of the heavy oil.
Sodium metal
in fact attacks the aromatic compounds in for example oil and forms electron
donor-
acceptor ion pairs, i.e., Nalaromaticr or (Na+)2[aromatic12- , which are
active for
hydrogen exchange reactions (Styles, Y. P.; Klerk, A. D., Energy Fuels 30,
5214-5222
(2016)). Moreover, one of the reaction products, sodium hydroxide (NaOH), is
the
chemical commonly used for alkaline flooding in oil fields, while the other
reaction
product, hydrogen gas (H2), may be further used in situ for gas flooding as
well as for
upgrading the heavy oil by a hydrogenation reaction when certain conditions
are met
(Gong, H. J.; Li, Y. J.; Dong, M. Z.; Ma, S. Z.; Liu, W. R., Colloids Surf. A
488, 28-35
(2016);Ramachandran, R.; Menon, R. K., Int. J. Hydrogen Energy 23, 593-598
(1998);
Teschner, D.; Borsodi, J.; VVootsch, A.; Ravay, Z.; Havecker, M.; Knop-
Gericke, A.;
Jackson, S. D.; Schlogl, R., Science 320, 86-89(2008)).
[0042] Furthermore, the reaction can be well controlled and initiated in situ
as
triggered following water injection, while the disappearance of the sodium
nanomaterials
after completion of the reaction eliminates the concern for permeability
damage
resulting from the adsorption and retention of nanomaterials.
[0043] Thus, in essence the high recovery performance is based the on reaction
between sodium and water, which allows the nanofluid to exhibit multiple
benefits in
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displacing subsurface oil. Substantial heat is released to raise the
temperature for
viscosity reduction. The generation of hydrogen gas helps to supply reservoir
energy
and to swell the heavy oil, as well as enabling possible oil miscibility and
upgrading
when certain criteria are met. Moreover, sodium hydroxide is produced to in
situ
synthesize surfactants for lowering interfacial tension and emulsification.
Multi-stage
nanofluid injection is found to be superior to a single-stage injection mode
since the
sweeping efficiency is improved.
Example 1: Sodium nanomaterial preparation (blending and ball-milling)
[0044] 1 gram of sodium metal was transferred to a ball milling jar with 40 mL
viscous
engine oil in the glove box. After high energy ball milling for a few hours,
the size of the
sodium metal particle was reduced to nanometer-micrometer, as shown in Fig. 1_
The
sodium particles were protected by the oil to avoid reaction with air and
moisture. In
order to reuse the engine oil, centrifugation was employed to separate the
sodium
particles from the engine oil as shown in Fig. 2.
[0045] Similarly, 2 grams of sodium metal were placed in a blender with 100 mL
of
mineral oil. After 15 minutes of blending, the size of the sodium metal was
reduced to
nanometer-micrometer. The sodium particles are protected by the oil avoiding
reaction
with air and moisture.
[0046] An organic solvent (pentane/hexane) was then used to disperse the
concentrated sodium metal particles as shown in Fig. 3. A hydrophobic polymer
with
high molecule weight may be added to the system for further stabilizing the
dispersion
of sodium particles and delaying the reaction with water.
[0047] After successful dispersion of the sodium metal particles, viscosity
reduction
experiments were performed. All experiments described herein were conducted at
room
temperature. The bottles were then placed in an oven at 65 C, which is
comparable to
the temperature of heavy oil wells_
[0048] Figure 4 shows an image of an original extra heavy oil. An extra heavy
oil
sample was used in a comparative study. As shown in Fig. 5, the original heavy
oil from
figure 4 is so sticky it could barely flow. Deionized (DI) water and the heavy
oil were
shaken together. The heavy oil stayed as a single piece. Due to the relatively
lower
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density of heavy oil than water, after settlement the heavy oil floats on the
water
surface. Then, engine oil was mixed into heavy oil and DI in water bottle.
[0049] After shaking and settlement, the oil viscosity changes due to the
miscible of
low viscous engine oil in heavy oil. However, the viscous heavy oil still
floats on the
water surface. In another bottle, NaOH was added into the heavy oil in DI
water
followed by shaking, the organic acids in the heavy oil could react with NaOH,
and thus
in some embodiments may generate surfactants which emulsify oil and water as
the
unclear water phase indicates. However, most of the viscous heavy oil remained
floating on the water surface. In comparison, a few drops of engine oil
dispersed sodium
particles were placed in the heavy oil and DI water bottle.
[0050] After treatment, the heavy oil becomes much more flowable and the
emulsion is
also produced as the yellow color in water phase indicates, and when the cap
is
opened, gas is released, wherein in some embodiments the air is H2 and air
that
expanded under a higher temperature caused by the heat generated by the metal
nano/micro particles. These observations indicate a reaction between the
sodium
particles and water which clearly helps to significantly reduce the viscosity
of oil and
improve flowability.
[0051] This process was repeated in a further embodiment, using saltwater
conditions
(e.g., 4 wt% NaCI water), and was found to aid extra heavy oil to flow, very
similar to the
case of DI water. To further compare the performance of pentane/hexane with
the
solution disclosed herein and as shown in Fig. 3, 1 mL pentane/hexane and the
solution
were separately added into two bottles which contain almost the same amount of
heavy
oil and DI water. As shown in Fig. 6, after treatment, the heavy oil may flow
for both of
the bottles, however, the bottle comprising the disclosed sodium particles
flows much
better, and clearly generates a milky-like emulsion which indicates the
generation of
surfactant by the reaction of NaOH with an add group(s) comprising the heavy
oil, and
thus the formation of an in situ emulsion provides a benefit of this method
for oil
recovery. Gas was again detectable by ear, on opening of the sealed reaction
bottle.
[0052] It was found that the oil treated as described herein, thus is much
less viscous
having a lower viscosity, hence the oil may be removed from the well formation
with
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greater ease due to its improved flowability as a result of treatment with the
particles
and methods described herein.
[0053] Thus, demonstrated in some embodiments herein, is a method to reduce
the
viscosity of a solution, such as but not limited to: heavy oil, in a further
embodiment a
method of extracting a solution such as but not limited to: heavy oil, or
extra heavy oil
from an underground formation is disclosed. In a further embodiment a method
of
making nanometer-micrometer sized highly reactive metal particles wrapped in a
polymer in an oil is disclosed, wherein the production of such particles is
both scalable
and economically viable.
[0054] In some embodiments, the particles may be easily injected into oil
wells for
reaction with water comprised within a well, and in some further embodiments
the
injection process may comprise one injection, or multiple injections.
[0055] The reaction with heavy oil comprising the well formation is highly
exothermic
(happens in situ (inside of) the well) and thus in other embodiments
significantly
increases the temperature so to reduce the viscosity of the heavy oil. As the
heat is
generated in situ when the composition meets with the oil/water, it is still
effective in
deep wells compared to compositions that react prior to being in situ of the
formation.
[0056] In some other embodiments, the particle reaction with water in situ of
the well
further produces metal hydroxide which may further react with organic acids in
the
heavy oil, and thus generates in situ surfactants that lower oil/water
interfacial tension.
[0057] In other embodiments, the metal particles may produce hydrogen gas in-
situ
(inside of) the well, which may be benefit for increasing reservoir energy,
cause a
viscosity reduction by the miscible with heavy oil, and upgrade oil quality by
inducing
hydrogenation reactions. Furthermore, in some embodiments the organic solvent
used
to disperse the high concentrated particles may also help to reduce the
viscosity of the
heavy oil comprising the well formation.
Example 2: Sodium Nanofluid Production
[0058] Large pieces of bulk sodium metal and silicone oil were purchased from
Sigma-
Aldrich and used as received. Three grams of sodium metal were mixed with 150
mL
silicone oil, which has a viscosity of 45.0-55.0 cP at 25 C. As shown in
Figure 1a, the
mixture was then transferred into the jar of a commercially available
Biolonnix G5200
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household blender For the first three minutes, the system was subjected to the
lowest
blending power to avoid strong collisions between the large pieces of sodium
and the
blender walls at high speed. Subsequently, the blender was used at its full
strength for
another 12 minutes. The entire process involves 15 minutes of blending with
some
additional cooling time after every five minutes of work to prevent the
blender jar from
cracking at high temperature. The final suspension displays a consistent grey
color as
shown in Figure 7b, indicating that the size of the sodium is reduced to the
nano to
micro scale. Colloidal stability of the nanofluid was evaluated since it is an
important
parameter for engineering screening and design. As indicated by the high
Hamaker
constants of metals, the van der Waals (VDW) interaction between two identical
metal
nanoparticles in a nonconductive medium would result in strong attraction
between the
nanoparticles, leading to an unstable system. According to theoretical
kinetics of
nanoparticles and/or nanosheets aggregation and Stoke's law for particle
settling, the
high viscosity of silicone oil and the density similarity between silicone oil
and sodium
metal contribute to delay such a phenomenon, helping to "kinetically
stabilize" the
system (Garnbinossi, F.; MyIon, S. E.; Fern, J. K., Adv. Colloid Interface
Sci. 222, 332-
349 (2015); Johnson, C. R; Li, X. Y.; Logan, B. E., Environ. Sci. Technol. 30,
1911-1918
(1996).
[0059] As shown in Figure 7 (b), after 24 hours of settling, the pure silicone
oil
suspension with a higher viscosity exhibits greater stability than that with
viscosity tuned
by using kerosene of 1.8 cP viscosity at the same nanomaterial concentration,
but both
systems have an adequate time window for surface injection before becoming too
unstable. The silicone oil suspension can even maintain colloidal stability
for more than
one week. It is also possible to further increase the stability by enhancing
the system
viscosity, such as by adding a soluble polymer.
[0060] X-ray powder diffraction (XRD) analysis was employed to confirm the
synthesized sodium nanomaterials. When XRD testing began, it was found that
the
sodium nanomaterials in the silicone oil would immediately read with the
environment
since the signature white color of sodium hydroxide was observed. This is
consistent
with the XRD patterns displayed in Fig. 7 (c) which show that both Na and NaOH
were
detected. However, by comparing the maximum peak values of Na and NaOH, it is
clear
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that Na is the majority component. To further demonstrate that X-rays could
activate the
reaction, multiple rounds of XRD testing was performed in order to calculate
the ratio of
the maximum peak values of Na and NaOH for each test, which was normalized
based
on the measurement results of the first test (see Fig. 10). As predicted, the
greater the
exposure to X-rays, the lower the ratio of Na to NaOH becomes. To obtain the
nanoparticles and/or nanosheets morphology and size information, atomic force
microscopy (AFM) was used to capture an image of the sodium nanomaterials in
silicone oil under a contact mode condition at room temperature. In order to
perform
AFM measurements in such viscous silicone oil maintaining the nanofluid as a
film of
less than 10 microns thick was found to be the key to obtaining a good image
and
eliminating viscous drag. As shown in Fig. 7d, the sodium nanomaterials
exhibit a sheet-
like structure, which is resulted from the shear force generated by the
blender, and the
morphology of sodium nanoparticles and/or nanosheets is controlled by the
forces
acting on the bulk sodium. The majority of the nanosheets have lateral
dimensions of
around 200 nm for the longer length and less than 100 nm for the shorter one.
In the
AFM imaging process, it was also found that the nanosheets have a strong
tendency to
aggregate into larger slices, from 300 nm in size to even much larger, due to
strong
VDW attraction. However, measurements of three different single sheets show
that they
have nearly the same thickness, of about 20 nm (such height profiles are shown
in Fig.
7d). The size distribution of the nanosheets was further investigated by light
scattering,
as shown in Fig. 7e, which displays a polydispersity in which most of the
particles are
less than 200 nm in diameter. This is in a good agreement with the results
from the
AFM.
Example 3: Sand-pack Experiments for Extra-heavy Oil Recovery
[0061] The highly viscous crude oil used for the following experiments is
shown as
photographed in Fig. 8 (a). Since viscoelasticity is characteristic of this
extra-heavy
crude oil, a rotational rheometer was employed to understand its behavior at
25 G. As
shown in Fig. 8 (b), both moduli depend on the frequency, and the loss modulus
exceeds the storage modulus, showing typical liquid behavior. Therefore, the
shear and
complex viscosities coincide no matter which part of the flow curve is
examined for
comparison (Ilyin, S. 0.; Stelets, L. A., Energy Fuels 32, 268-278 (2018)).
Based on
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this analysis, the viscosity of the crude oil is over 400,000 cP, placing it
in the category
of extra-heavy oil. It is exceedingly difficult to use porous rocks to perform
the recovery
tests without damaging the oil's chemical properties. Sand-pack flow
experiments, as
schematically illustrated in Fig. 8 (c), were therefore conducted using
spherical
zirconium oxide (ZrO2) balls with a uniform diameter of 0.5025 cm as packing
sands.
The dimensions of the packed column were chosen as length of 7 cm and diameter
of
2.765 cm (Dan Luo, Zhifeng Ren, Synthesis of sodium nanoparticles for
promising
extraction of heavy oil, Materials Today Physics, Volume 16, 2021, 100276.).
[0062] Porosity and Permeability Calculations: with the assumption of ideal
packing,
the porosity and permeability can be calculated using empirical equations
(Dixon, A. G.,
Can. J. Chem. Eng. 66, 705-708 (1988), Li, Y. C.; Park, C. W, Ind. Eng. Chem.
Res.
37, 2005-2011 (1998)): for spherical particles of identical size not mixed
with extra-
heavy oil, the porosity ch is calculated by
01 = 0.4 + 0.05 (dt
- 3) + 0.412 Edp)2 0.5,
dt
r
where dp is the diameter of a spherical particle while dt is the diameter of
the packed
column. When extra-heavy oil is mixed with the particles, the porosity 02 is
given as
vtotumn*01-Thipo
02 ¨
ilcolumn
where A/column is the volume of the packed column, mo is the mass of the extra-
heavy
oil, and po is the density of the extra-heavy oil. According to the Kozeny-
Carman
correlation, the permeability k is given as
k = 2P
330(1-02)2 =
[0063] Based on the above equations, the physical properties of the sand-pack
columns used for the five experiments are displayed below in Table 3. The
recovery
performance of a single-stage sodium nanofluid injection was first tested with
different
nanofluid concentrations at 25 C. Since water flooding is usually implemented
after
primary recovery utilizing natural pressure difference, it was also injected
here first as
well for comparison. To delay the reaction between the sodium nanofluid and
the pre-
existing water, a small amount of Crown 1-K kerosene was used as a pre-flush
fluid
prior to injection of the nanofluid. After finishing the nanofluid injection,
kerosene was
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also used as a post-flush fluid to clean the residue in the pipeline, followed
by another
water injection to trigger the reaction. The detailed injection procedures,
rates, and
material amounts are provided herein, and the column porosity and permeability
are
provided in Table 3. For each sand-pack test, the sodium nanomaterials were
dispersed
in a solvent with 1:1 volume ratio of silicone oil to kerosene. The recovery
efficiency is
calculated as:
efficiency.% = (1 mass of sandpack colunm after injection) X 100%.
original mass of san pack colunm
As indicated by the recovery results provided in Table 1, pure water injection
does not
play any role in this highly viscous oil recovery This agrees with the usual
extremely low
recovery performance by water flooding in actual extra-heavy oil reservoirs.
However,
significant recovery improvement was detected when sodium nanofluid was used
at
each tested concentration.
Table 1. I Extra-heavy oil recovery performance by single-stage nanofluid
injection with
different concentrations at 25 C.
Concentration of
As-received extra-
Recovery efficiency of
Test y oil
sodium nanosheets
Recovery efficiency of
heav in column, in 5 mL nanofluid water
injection before
nanofluid, %
gram nanofluid, %
injection, mg
1 9.99 200
0.0 30.7
2 9.50 400
0.0 51.9
3 8.79 800
0.0 40.1
[0064] In observing the change in recovery efficiency by tuning the amount of
nanomaterials, it is interesting that increasing the nanomaterial
concentration does not
always further increase the efficiency, which is different from our assumption
that more
sodium nanomaterials would generate more heat for greater reduction of
viscosity,
allowing the oil to flow more easily. The explanation for these results is
discussed in the
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section below on the interactions between the oil and the nanofluid. In
addition, the
control experiment using only solvent without nanomaterials for recovery is
listed as
Test 5 in Table 2, which shows that it can only achieve 6.2% recovery
efficiency in the
first stage. This comparison clearly demonstrates that sodium nanosheets play
a major
role in the recovery of this extra-heavy oil.
[0065] To further develop its potential for recovery, a multi-stage injection
of sodium
nanofluid, was performed and the results of which are shown as Test 4 in Table
2.
Based on the results from the single-stage injection experiments, the
conditions in
Stage I of Test 4 are the same as those of Test 2, using 400 mg sodium
nanosheets.
This was followed by another two stages of alternating injections of water and
1 mL
nanofluid containing 100 mg sodium nanosheets. Detailed information regarding
the
injection procedures, as well as those for the solvent-only control test, are
provided in
the Experimental Section below. Table 2 shows that multi-stage injections can
further
enhance the recovery efficiency even for the case of only solvent.
Significantly
distinguished from the multi-stage solvent-only injections, three stages of
sodium
nanofluid injections resulted in a very high recovery efficiency, i.e., 81.6%,
which is also
indicated by the surface color change of the ZrO2 balls from shiny black to
their original
white (see Fig. 11). Generally, in comparison with a single-stage injection,
the
distribution of fluids by multi-stage injections in the sand-pack column is
different, even
when the same amount of material is used.
Table 2. I Extra-heavy oil recovery performance by multi-stage nanofluid
injections at
25 C.
Recovery
As-received efficiency of
I
Stage Stage
Test extra-heavy oil water injection
Stage
efficiency, % efficiency, % efficiency, %
in column, gram before
nanofluid, %
4 (nanofluid) 9.38 0
53.9 71.6 81.6
10.17 0
6.2 11.3 15.5
(solvent)
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Interactions between Extra-heavy oil and Nanofluid
[0066] Investigating the interactions between the oil and the sodium nanofluid
is
fundamental to understanding the mechanisms underlying oil recovery by these
reactive
nanosheets. It is well known that an alkali metal reacting with water is a
strong
exothermic process and could lead to an explosion.31 The change of enthalpy
for this
type of reaction between sodium and water is -184 kJ/mol at standard
conditions. In a
straightforward way, such released heat could be used to increase the
temperature of
extra-heavy oil. To demonstrate this effect, an apparatus was built, and the
results are
shown in Fig. 9 ((a) and (b)). Initially, 1gram extra-heavy oil was mixed with
40 mg
sodium nanosheets dispersed in 0.5 mL pure kerosene. A thermometer was placed
into
the extra-heavy oil, displaying its initial temperature as 20.7 C. Triggered
by 0.3 mL
water injection, a temperature difference of nearly 30 C can be achieved even
in such
an open system. Ideally, if there is no heat generation by sodium hydroxide
dissolution
in water or heat loss through convection by hydrogen gas, conduction by the
glass vial,
etc., the calculated temperature difference can reach 85 it as shown in the
Supplementary Information. In addition to the rise in temperature, another
easily
observable phenomenon was the generation of bubbles in the vial due to the
production
of hydrogen gas. Therefore, another demonstration was performed to show the
effect of
such gas production on the extra-heavy oil. By mixing 1 gram extra-heavy oil
with
sodium nanofluid as shown in Fig. 9 (c), sodium nanosheets were evenly
distributed
throughout the extra-heavy oil since the solvent (kerosene/silicone oil at 1:1
volume
ratio) could dissolve this crude oil. Following injection of water, hydrogen
gas was
generated (see Video S1 in the Supplementary Information), and the extra-heavy
oil
began to swell.
[0067] After a noticeably short time, the oil expanded to the edge of the
Petri dish as
shown in Fig. 9 (d). In a confined system or in rock pores at reservoir
conditions, the
generation of hydrogen gas directly supplies the reservoir with energy for oil
recovery.
The swelling of the extra-heavy oil also contributes to its recovery. In
addition, it is also
possible that hydrogen gas could be miscible with the oil once the local
pressure is over
the minimum miscibility pressure (MMP), like the carbon dioxide, flue gas,
nitrogen gas,
methane, etc. used in miscible flooding. Using this miscibility, the viscosity
of the extra-
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heavy oil could also be largely reduced. It must also be mentioned here that
the
alternating injections of sodium nanofluid and water in the multi-stage mode
in fact
generate water-alternating-gas (WAG) flooding, which has been demonstrated to
significantly modify sweeping efficiency in practice in the field. Since the
recovery
efficiency is equal to the product of the sweeping efficiency and the
microscopic
displacement efficiency, the improved sweeping efficiency is one of the main
reasons
that multi-stage injections can achieve higher efficiency than the single-
stage mode,
even when the same amount of material is injected (Shah. A.; Fishwick, R.;
Wood, J.;
Leeke, G.; Rigby, S.; Greaves, M., Energy Environ. Sci. 3, 700-714 (2010);
Zhou, X.;
Yuan, Q. W.; Peng, X. L.; Zeng, F. H.; Zhang, L. H., Fuel 215, 813-824(2018);
Al-Bayati,
D.; Saeedi, A.; Myers, M.; White, C.; Xie, Q.; Clennell, B., J. CO2 Util. 28,
255-263
(2018)).
[0068] Mother important product resulting from the reaction between the sodium
nanosheets and the water is sodium hydroxide since it has been recognized to
react
with organic acids in crude oil to in situ generate surfactants, which has
been put into
practice in actual oil fields for many years. As a result, several oil
recovery mechanisms
have been identified, including the lowering of interfacial tension (IFT),
emulsification of
the oil, and wettability alteration. These three mechanisms are believed to
increase the
microscopic displacement efficiency, while emulsification can further improve
the
macroscopic sweeping efficiency by diverting flow (Mason, P. E.; Uhlig, F.;
Vane*, V.;
Buttersack, T.; Bauerecker, S.; Jungwirth, P., Nat. Chem. 7, 250-254 (2015);
Zhang, H.
Y.; Dong, M. Z.; Zhao, S. Q., Energy Fuels 26, 3644-3650 (2012); Pei, H. H.;
Zhang, G.
C.; Ge, J. J.; Jin, L. C.; Liu, X. L., Energy Fuels 25, 4423-4429 (2011);
Kumar, S.;
Mandal, A., Appl. Surf. Sci. 372, 42-51 (2016)).
[0069] Since there is an optimal alkaline concentration at which the IFT
reaches a
minimum, a series of experiments as shown in Fig. 12 (a) were conducted to
investigate
the effect of nanosheet concentration on the interactions among the extra-
heavy oil,
water, and sodium nanosheets_ 1g of extra-heavy oil was mixed with different
concentrations of sodium nanosheets dispersed in 0.5 mL silicone/kerosene (1:1
volume ratio), followed by injection of 0.3 mL water to trigger the reaction
at room
temperature. After some time, 9.7 mL water was injected, and the fluid system
was
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shaken by hand. All the chosen concentrations showed the ability to emulsify
the extra-
heavy oil, but the emulsion remained stable for at least one week at room
temperature
only in the sample with 40 mg nanosheets. The emulsion type was determined to
be oil-
in-water since the emulsion droplets maintain their shapes in the oil phase as
shown in
the inset of Fig. 12 (b). An optical microscope was further employed to
measure the
emulsion size. As shown in Fig. 12 (b), the emulsion diameters range from
several
microns up to 15 pm. In fact, there are two types of emulsions. The
transparent droplets
observed in Fig. 12 (b) are kerosene or silicone oil used as solvent for the
nanofluid
while the dark, opaque droplets are the extra-heavy oil. The emulsified system
exhibits
extremely low viscosity, i.e., 1.31 cP, as the water is the bulk phase. For
the most stable
emulsion found here, formed using 40 mg nanosheets, the sodium hydroxide
concentration after completion of the reaction is about 0.69 wt%, which is
very close to
the reported optimal NaOH concentration to achieve a minimum IFT (Zhao, C. M.;
Jiang,
Y. L.; Li, M. W.; Cheng, T. X.; Yang, W. S.; Zhou, G. D., RSC Adv. 8, 6169-
6177 (2018).
[0070] To measure the oil viscosity, the fluid was demulsified in the system
by adding 2
wt% NaCI and maintaining the system at 50 C overnight. After cooling the
system down
to 25 C, it exhibited a phase separation as shown in Fig. 12 (c). The top
layer is
colorless light oil with measured viscosity of 1.84 cP and the bottom layer is
water The
as-received extra-heavy oil was modified through interactions with the sodium
nanofluid
and accumulated in the middle layer. Its viscosity was sharply reduced to
259.60 cP
from its initial viscosity of over 400,000 cP. The above results show that the
optimal
concentration of nanofluid for the extra-heavy oil recovery was found in the
previous
sand-pack experiments.
Experimental Section
[0071] Materials. The extra-heavy oil was provided by a commercial oil
company.
Large sodium pieces were purchased from Sigma-Aldrich and stored in kerosene
with >
99.8% purity. Silicone oil with a viscosity of 45.0-55.0 cP (25 C) and a
density of 0.963
g/mL (25 C) and sodium chloride of ACS reagent grade were also purchased from
Sigma-Aldrich. Kerosene of grade K-1 used in all experiments was distributed
by Crown
and purchased from Walmart_ All the chemicals were used as received_ Water
used in
all experiments was deionized and has a resistivity of 18.2 million ohm-cm.
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[0072] Instruments and Characterization. A Biolomix household blender (model
number G5200) was used to produce the mixtures of sodium nanosheets and
silicone
oil. It has a maximum of 2200 W motor power, allowing its mixing blades to
reach up to
45,000 RPM. A Panalytical X'pert PRO diffractometer was employed to conduct X-
ray
diffraction (XRD) measurements at atmosphere. The samples analyzed by XRD are
the
suspensions of sodium nanosheets dispersed in silicone oil. As the
measurements were
taken, it was clear that X-rays activate the sodium nanosheets to react with
water in the
atmosphere since white crystal powder and bubbles appeared, indicating the
presence
of sodium hydroxide and hydrogen gas, respectively. The atomic force
microscope
(AFM) used in the experiment is a Multimode 8 system under a contact mode
condition
with NanoScope 8.15 control software. The AFM probes used are MLCT probes from
Bruker Nano. The spring constant of the AFM cantilever is 0.02 N/m. The low-
concentration sodium nanosheet sample was prepared in silicone oil at room
temperature.
[0073] A 2 pl drop of the sample was applied onto a newly cleaved mica (Ted
Pella
Inc.) surface, and a lens paper (Thermal Fisher Inc.) was immediately used to
remove
excess silicone oil from the mica to maintain a maximum oil-film thickness of
less than
pm. A quick image scan was used with a frequency of 3Hz. In the AFM imaging
process, it was noticeable that the sodium nanosheets have a strong tendency
to
aggregate into a larger slice. The size distribution of the nanosheets was
further
detected by the light scattering method using a Malvern NanoSight NS300. The
nanosheets were dispersed in kerosene at a very dilute concentration for light
scattering
measurements. A TA Instruments rheometer was used to probe the viscoelasticity
of the
as-received extra-heavy oil. The oil was first placed on the parallel plate,
followed by
slowly lowering the top plate until the gap was fully filled. An amplitude
sweep was
conducted to determine the linear viscoelastic region. A frequency sweep from
0.1 to
100 rad/s was then completed using a strain in the linear region at room
temperature.
The changes in storage and loss moduli, as well as in the complex viscosity,
with
frequency could thus be obtained. The viscosity of the extra-heavy oil
following the
reaction with sodium nanofluid was measured using a TQC Sheen cone and plate
viscometer. The size of the emulsion droplets was observed using an optical
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microscope.
[0074] Sand-pack Experiments. The sand-pack flow system mainly consists of a
pump, a sand-pack column holder, a collector, and three containers that are
used to
store deionized water, kerosene, and sodium nanofluid. The sands used in all
experiments are white zirconium oxide (ZrO2) balls with a diameter of 0.5025
cm. The
sands were evenly mixed with certain amounts of extra-heavy oil. The packed
column is
7 cm in length and 2.765 cm in diameter. The two injection modes, single-
stage, and
multi-stage, were tested to evaluate the extra-heavy oil recovery performance
at 25 C.
[0075] Single-Stage Injection. Three different concentrations of sodium
nanofluid
were used in the tests, including 200 mg, 400 mg, and 800 mg sodium nanosheets
in 5
mL solvent (silicone oil/kerosene at 1:1 volume ratio). Following preparation
of the sand-
pack column, water was first injected at 0.05 mUmin until no oil came out,
followed by
injecting 1 mL kerosene as the pre-flush liquid at a higher rate, i.e., 0.5
mUmin. Sodium
nanofluid was then injected at 0.1 mL/min. This was followed by a post-flush
fluid of 1
mL kerosene injected to displace any possible residue nanofluid in the
pipeline. To
trigger the reaction, water was again injected at 0.05 nriUrnin until no oil
came out.
Table 3. Porosity and permeability of each sand-pack column.
Test Porosity, %
Permeability, D
1 19.7
2.00 x 103
2 21.3
2.63 x 103
3 18.5
1.60x 103
4 19.9
2.07 x 103
18.1 1.49 x 103
Temperature Difference Calculations
[0076] At standard conditions, the heat released by sodium reacting with water
is -184
kJ/mol. Our experimental system initially consisted of 1-gram extra-heavy oil
and 40 mg
sodium nanosheets dispersed in 0.5 mL pure kerosene, followed by injection of
0.3 mL
water Without considering any heat loss or sodium hydroxide dissolution in the
water,
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ideally obtain the following equation:
184 * ¨
nriNa . AT .ittl-' Jen
0 * MO 1- Cpw * Mw 1- Cpk * Mk I- CpNaOH * mNaOH 1- CpH2 * MHO'
P
P4Na
where mNa is the mass of sodium, 40 mg; MNa is the molecular weight of sodium,
23
g/mol; AT is the temperature difference in C; Cpa is the specific heat
capacity of extra-
heavy oil, 1.69 kJ/(kg* C);3 1110 is the mass of extra-heavy oil, 1 gram; C.
is the specific
heat capacity of water, 4.19 kJ/(kg* C):4 mw is the mass of the water
reaction, 0.269
gram here; Cpk is the specific heat capacity of kerosene, 2.01 kJ/(kg* C);4
CpNaoH is the
specific heat capacity of NaOH, 59.92 J/(mol* C);5 rn
¨NaOH is the mass of NaOH; CpH2 is
the specific heat capacity of H2, 14.31 kJ/(kg* C);6 mh, is the mass of H2.
All the
specific heat data used are at 25 C. As a result, the temperature difference
can reach
to about 85 C.
[0077] Multi-Stage Injection. Based on the results from the single-stage
injection
experiments, 5 mL sodium nanofluid containing 400 mg sodium nanosheets as the
first
stage of the multi-stage injection experiment were used. The procedures of the
first
stage are the same as those for the single-stage mode. The first stage was
followed by
injection of 1 mL sodium nanofluid containing 100 mg sodium nanosheets and
subsequent injection of water at a rate of 0.05 mL/min until no more oil came
out,
completing the second stage. Finally, another 1 mL sodium nanofluid containing
100 mg
sodium nanosheets was injected, followed by water injection at 0.05 mUmin
until no
more oil came out. In total, three stages of nanofluid injections were
conducted.
Furthermore, a control experiment was also performed, in which the same
procedures
were used as in the three-stage experiment, except that the sodium nanofluid
was
replaced by the solvent used for dispersing the sodium nanosheets.
[0078] In conclusion, disclosed herein is a fast and inexpensive method to
synthesize
nanosheets for the reduction of viscosity of solutions, such as but not
limited to heavy
oil, for reduction of viscosity therefore and subsequent extraction from a
body, for
example a well formation, or a hydrocarbon bearing formation. Sodium
nanosheets may
be simply produced by using a household blender. A colloidally and chemically
stable
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sodium nanosheet fluid was formed and demonstrated in situ recovery of highly
viscous
crude oil at room temperature. By investigating the interactions among extra-
heavy oil,
sodium nanofluid, and water, multiple benefits were revealed to contribute to
such oil
recovery and are based on the chemical reaction between alkali metal and
water. In
sand-pack experiments, it was found that a multi-stage injection mode is
superior to a
single-stage mode in the recovery since higher sweeping efficiency can be
achieved.
However, no two crude oil deposits are exactly the same, and reservoir
conditions vary
widely around the world. Optimal concentrations of sodium nanofluid in actual
oil fields
would therefore vary. The nanofluids disclosed herein are applicable to
address
recovery issues for conventional light oil due to its benefits of gas
generation, IFT
reduction, emulsification of crude oil, etc. It may also have potential for
extracting oil
from oil sands. In addition, it is possible to mix the sodium nanosheets with
other
chemicals commonly used in oil fields, such as surfactants and polymers, for
other
applications. More importantly, sodium resources are abundant and the method
to make
sodium nanosheets is scalable and environmentally friendly. Massive studies on
the
application of nanotechnology in petroleum industry especially for EOR have
been done
and shown promising results. Nano-EOR is proposed to substitute the existing
chemical
EOR for improving the oil recovery efficiency with several advantages: (1)
Nanoparticles
and/or nanosheetss can improve the fluid performance by only using small
amount of
materials, (2) improvement in heat and mass transfer lead to the possible
application in
high-temperature condition, (3) high flexibility for combining with other
materials such as
surfactant and polymer. Various types of Nanoparticles and/or nanosheetss
(organic
and inorganic) are confirmed to be able to significantly increase the oil
recovery.
Nanoparticles and/or nanosheets can improve the oil recovery through several
mechanisms such as interfacial tension reduction, wettability alteration,
disjoining
pressure, and viscosity control. Some parameters, like nanoparticles and/or
nanosheets
concentration, size, temperature, wettability, and salinity, are proven to
affect the
performance of nano-EOR.
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